1. Field of the Invention
The present invention relates generally to web printing presses and more particularly to a cutting and diverter unit for a web printing press as well as to a method for cutting a web and diverting the resultant signatures into two streams.
2. Background Information
Web printing presses print a continuous web of material, such as paper. The continuous web then is cut in a cutting unit so as to form signatures which can then be folded in a folder or arranged in different manners. In order to arrange signatures in a desired fashion or to permit desired folds, the signatures often may be diverted into two streams, for example, and also may be decelerated.
U.S. Pat. No. 5,607,146 discloses a mechanism for diverting of products in a folding apparatus. A pair of cutting cylinders cuts the web, so that signatures are accepted by a pair of transport belts. Each transport belt has a raised surface which interacts with a non-raised surface of the other belt. The raised surfaces of the belts thus cause each signature to be diverted off a center line in alternating fashion, so that one signature is offset slightly to the left side and the next slightly to the right side. The signatures then are directed to past a guide member depending on whether the signatures are offset to the left or to the right to pockets of side-by-side fan wheels, so that the right fan wheel accepts a signature diverted to the right and the left fan wheel accepts the next signature, which is diverted to the left. The terms xe2x80x9crightxe2x80x9d and xe2x80x9cleftxe2x80x9d are used here for descriptive purposes only. The signatures are thus split into two streams by the fan pockets.
U.S. Pat. No. 5,615,878 discloses a cutting device which fully cuts a web into signatures, which then are accepted by two transport belts having interlacing raised sections. The raised surfaces of the belts thus cause each signature to be diverted off a center line in alternating fashion, so that one signature is offset slightly to one side into a first fan and the next slightly to the other side into a second fan. The first and second fans are located side-by-side and their fan blades overlap.
U.S. Pat. No. 5,702,100 also discloses a cutting device for cutting a web into signatures that are accepted by transport belts. Two diverting elements divert each signature into one of two side-by-side fans.
The devices of the above-cited patents have the disadvantage however that the signatures are fully cut far away from the belts, which can lead to a poor cutting device-to-tape transfer. Also the top ends of the signatures are poorly supported. These disadvantages can lead to signatures being damaged or not properly diverted. Moreover, the signatures are diverted using side-by-side devices, which can require substantial and often valuable floor space.
An object of the present invention is to provide a reliable device and method for diverting signatures. An alternate or additional object of the present invention is to reduce floor space requirements for a diverter.
The present invention provides a method for cutting a web and diverting signatures which includes the steps of partially cutting the web so as to form a partially cut web section; cutting the partially cut web section with a cutting device so as to form signatures; passing a first belt through at least a part of the cutting device; and holding the signatures between the first belt and a second belt so that the signatures are offset in an alternating fashion to define a first stream and a second stream of the signatures.
The present method advantageously provides a double-cut configuration which can allow for holding of the signatures closer to the last cut so that when the web is cut into signatures, it may be held firmly in place by the pair of belts. Tension and proper placement may be maintained at all times even as the web is cut. The resultant diverting of the signatures thus also may be performed effectively.
Preferably, the method may include matching a lead edge of the signatures with a rear edge of a raised section of one of the belts at the cutting device. This procedure allows for close placement of the belts near the cutting operation, which with the single cut devices of the prior art was difficult or impossible to achieve.
Advantageously, after the signatures are offset to define first and second streams, the first stream and second stream of signatures may be gripped respectively by a first delivery device and a second delivery device, which may be, for example, deceleration devices.
In accordance with a further embodiment of the present invention, the delivery devices may be located one above the other to reduce floor space. Preferably, when the delivery devices are located one above the other the first stream of signatures are offset in a first direction, gripped by the first delivery device, released by the second belt moving away and then supported by a first signature support. The second stream of signatures may be offset in a direction opposite the first direction so as to pass by the first signature support. The first belt and a back side of first signature support then may be used to further support the second stream of signatures. The second stream of signatures then may be gripped by a third belt and the first belt and transported to the second delivery device.
The present invention also provides a diverter which includes a first cutting device for partially cutting a web; a second cutting device downstream of the first cutting device for fully cutting the web so as to form a plurality of signatures; and at least one first belt and at least one second belt for holding the plurality of signatures, the first belt having at least one first raised outer section and passing through at least part of the second cutting device, the second belt having at least one second raised outer section, the first and second raised outer sections interacting to offset the plurality of signatures so as to define an alternating first stream and second stream of the plurality of signatures.
One advantage of the present device is that tension and proper signature placement may be maintained during cutting by having the two cutting devices and the first belt passing through at least part of the second cutting device, and that the resultant offsetting provides effective diverting of the signatures. Advantageously, both of the first and second belts may pass entirely through the second cutting device to aid in holding the signatures just after they are cut.
Advantageously, more belts than just the first belt and the second belt are provided so as to define a plurality of paired belts spaced apart from one another. The second cutting device may include a plurality of cutting disks spaced apart from one another so as to define non-cut spaces. The paired belts advantageously pass through the non-cut spaces in the second cutting device.
Advantageously, a first delivery device receives the first stream of signatures; and a second delivery device receives the second stream of signatures.
The first delivery device preferably has a first signature support for supporting the signature after the signature is not longer held by the first and second belt. The first signature support may have a support side with a curved section and a straight rear side, which advantageously may support signatures of the second stream before those signatures are held between the first belt and a third belt, or are delivered directly to the second delivery device. The third belt may begin within cut-out regions at the rear of the signature support of the first delivery device.
The first and second delivery devices advantageously are gripper deceleration devices which can-slow down the rate of delivery of the signatures.
The present device is particularly advantageous for use with high-speed web printing presses, e.g. presses operating at over 2000 feet per minute, since the signatures are held firmly at all times.
The present invention also provides a floor-space-saving diverter comprising a cutting device for cutting a web so as to form a plurality of signatures, a first belt and a second belt with raised outer sections interacting to offset the plurality of signatures so as to define an alternating first stream and second stream of the plurality of signatures, a first delivery device for accepting the first stream; and a second delivery device located below the second delivery device for accepting the second stream.